Internal combustion engine systems may operate a series of gas exchange valves in each cylinder of the engine to provide gas flow through the cylinders. One or more intake valves open to allow charge air with or without fuel to enter the cylinder while one or more exhaust valves open to allow combusted matter such as exhaust to exit the cylinder. Intake and exhaust valves are often poppet valves actuated via linear motion provided directly or indirectly by cam lobes attached to a rotating camshaft. The rotating camshaft may be powered by an engine crankshaft. Some engine systems variably operate the intake and exhaust valves to enhance engine performance as engine conditions change. Variable operation of the intake and exhaust valves along with their respective cam lobes and camshafts may be generally referred to as cam actuation systems. Cam actuation systems may involve a variety of schemes such as cam profile switching, variable cam timing, valve deactivation, variable valve timing, and variable valve lift. As such, systems and methods for cam actuation systems may be implemented in engines to achieve more desirable engine performance.
In one approach to provide a cam actuation system, shown by Rauch and Proschko in U.S. Pat. No. 8,020,526, a hydraulic variable valve train is provided to vary the control times and lifting strokes of the gas-exchange valve attached to the variable valve train. This system utilizes a series of hydraulic passages, chambers, accumulators, pistons, and a hydraulic valve to activate the gas-exchange valve. A cam rotates against a pump tappet to pressurize hydraulic fluid in order to actuate a slave piston to move the gas-exchange valve.
However, the inventors herein have recognized potential issues with the approach of U.S. Pat. No. 8,020,526. First, the variable valve train system described in U.S. Pat. No. 8,020,526 may be used primarily for variable valve lift which may require a fast-acting solenoid valve precisely timed to rotation of the engine crankshaft to allow for correct valve event timing. If the solenoid valve were to be mis-timed by a small amount, then the valve events may not be properly timed which may lead to less than desired engine performance. Furthermore, the variable valve train system indirectly conveys motion to the gas-exchange valve by first providing actuation to a pump tappet before transferring the motion to the slave piston. Indirect actuation of the gas-exchange valve via additional components may create higher risk for valve degradation.
Thus in one example, the above issues may be at least partially addressed by a poppet valve operator, comprising: a rocker arm including a poppet valve engaging end and a camshaft engaging end, the rocker arm including a pivot pocket positioned between the camshaft engaging end and the poppet valve engaging end; and a hydraulically operated pivot ball selectively engaging the pivot pocket. In this way, the rocker arm may directly couple to both a cam lobe of a camshaft and a hydraulically operated pivot ball. The pivot ball may further be attached, e.g., directly, to a stem of a piston contained in a housing, wherein the piston may be selectively rigidly or flexibly held in place by hydraulic fluid provided by an external system such as an engine oil pump. With a solenoid valve and accumulator, when valve deactivation is desired, the solenoid valve may be operated at a slower speed than required for the hydraulic valve of U.S. Pat. No. 8,020,526.
In one example, the poppet valve operator may be implemented as a hydraulic rolling cylinder deactivation system, wherein engine displacement is varied by selectively opening and closing a number of intake and exhaust valves, which are often poppet valves. In other examples, the poppet valve operator may be used to actuate variable valve lift or variable valve timing methods. Furthermore, the poppet valve operator may control more than one poppet valve with a single control system comprising of an accumulator and solenoid valve, among other components. Further still, the poppet valve operator may be equipped with a latch pin for reducing leaked oil or other hydraulic fluid when the engine is shut down and pressurized oil is no longer provided to the poppet valve operator. As such, it may be possible to increase available packaging space around the engine by controlling multiple poppet valves with the single control system. Also, including the latch pin may increase the response time of the variable valve lift method upon restarting the engine since the amount of leaked oil may be reduced.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.
While FIGS. 2-3, and 5-12 are not drawn exactly to scale, the drawings may represent example relative positioning of various components with respect to each other, such as axially above or below each other, etc.